The present invention relates to liposome encapsulated drugs and delivery systems, specifically liposome encapsulated cisplatin. The drugs are useful to kill cancer cells in a variety of human malignancies after intravenous injection.
Throughout this application various publications, patents and published patent specifications are referenced by author and date or by an identifying patent number. Full bibliographic citations for the publications are provided within this disclosure or immediately preceding the claims. The disclosures of these publications, patents and published patent specifications are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
Cis-diamminedichloroplatinum(II), cis-[Pt(NH3)2Cl2]2+, abbreviated cisplatin or cis-DDP, is one of the most widely used antineoplastic drugs for the treatment of testicular, ovarian carcinomas and against carcinomas of the head and neck. More than 90% of testicular cancers are cured by cisplatin. The most severe side effects are nephrotoxicity, bone marrow toxicity and gastrointestinal irritation (Oliver and Mead, 1993). Bilateral optic neuropathy was observed in a patient affected by ovarian carcinoma treated with 160 mg/m2 cisplatin and 640 mg/m2 carboplatin (Caraceni et al., 1997). Oral hexamethylmelamine treatment in a group of 61 patients with epithelial ovarian carcinoma with cis- or carboplatin resistance (relapse within 6 months after the end of that therapy) showed a 14% objective response rate (Vergote et al., 1992).
Cationic cholesterol derivatives have been used to deliver therapeutic agents. For example, they have been mixed with phosphatidylethanolamine and sonicated to form small unilamellar vesicles which can complex with DNA and mediate the entry into the cytosol from the endosome compartment. One of the liposome formulations, DC-Chol liposomes, has been used in a gene therapy clinical trial against melanoma. Human immunodeficiency virus-1 transactivating protein gene was codelivered with a reporter gene under the control of HIV-1 long terminal repeat. Human tumor cells selected for cisplatin resistance or isolated from patients who had failed cisplatin therapy were highly transfectable with cationic liposomes. These results suggested a serial therapy protocol with cisplatin and gene therapy for malignancy (Farhood et al., 1994).
Various platinum complexes prepared from 2-amino-methylpyrrolidine derivatives as carrier ligands were tested for their antitumor activity against Colon 26 carcinoma and P388 leukemia using subcutaneous and/or intraperitoneal injections in mice. 2-aminomethylpyrrolidine proved to be the most effective carrier ligand in its amine derivatives (Morikawa et al., 1990).
An optimum procedure was established by orthogonal test for preparing cisplatin albumin microspheres (Cis-DDP-AMS) with emulsion-heating stabilization method (mean size was 148 microns). The distribution and elimination half times of platinum were prolonged 3.36 times and 1.23 times after hepatic arterial chemoembolization with Cis-DDP-AMS versus Cis-DDP, respectively (Zhang et al., 1995).
The search for platinum (II)-based compounds with improved therapeutic properties was prompted to design and synthesize a new family of water-soluble, third generation cis-diaminedichloroplatinum (II) complexes linked to uracil and uridine. However, none of the synthesized compounds showed any significant cytotoxic activity against three cell lines that were treated (Kim et al., 1998).
The recently developed bioreductive agent 4-[3-(2-nitroimidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1) was found to potentiate the antitumor effect of the chemotherapeutic agents melphalan (L-PAM), cisplatin (cisDDP) and cyclophosphamide (CPM) without concurrent enhancement in bone marrow toxicity. Potentiation was strictly schedule dependent and the optimum effect (1.5 to 2 logs killing beyond additivity) was observed when NLCQ-1 was given 45-min before cisDDP. These results support the classification of NLCQ-1, based on clinical studies, as a chemosensitizer (Papadopoulou et al., 1998).
A combination of paciltaxel with cisplatin as second-line treatment in patients with non-small cell lung cancer (NSCLC) who had previously undergone first-line therapy with cisplatin achieved partial response (40%) in 14 patients (Stathopoulos et al., 1999).
Abra et al. (U.S. Pat. No. 5,945,122, issued Aug. 31, 1999) describes a liposome composition containing entrapped non-charged cisplatin in mostly neutral lipids. However, the process of Abra et al. uses neutral lipids compared with the anionic lipid DPPG disclosed in the present patent for cisplatin entrapment.
Thus, while the prior reports indicate that liposome mediated delivery of cisplatin and other therapeutic drugs is possible, therapeutic efficiency has been limited by the low aqueous solubility and low stability of cisplatin. Therapeutic efficacy also is limited by the high toxicity of the drug. Thus, a need exists to reduce the difficulties involved in processing of cisplatin containing drugs and high toxicity of cisplatin when used therapeutically. This invention satisfies this need and provides related advantages as well.
In one aspect, this invention provides a method for encapsulating cisplatin and other positively-charged drugs into liposomes having a different lipid composition between their inner and outer membrane bilayers and able to reach primary tumors and their metastases after intravenous injection to animals and humans. In one aspect, the method includes complex formation between cisplatin with DPPG (dipalmitoyl phosphatidyl glycerol) or other lipid molecules to convert cisplatin to its aqua form by hydrolysis which is positively-charged and is the active form of cisplatin endowed with the antineoplastic activity. At this stage membrane fusion peptides and other molecules with fusogenic properties may be added to improve entrance across the cell membrane of the complex. The aqua cisplatin-DPPG micelles are converted into liposomes by mixing with vesicle forming lipids such as pre-made liposomes or lipids followed by dialysis and extrusion through membranes, entrapping and encapsulating cisplatin to a very high yield. Doxorubicin or other positively-charged compounds can be substituted for cisplatin in these formulations. The encapsulated cisplatin has a high therapeutic efficacy in eradicating a variety of solid human tumors including but not limited to breast carcinoma and prostate carcinoma. Combination of the encapsulated cisplatin with encapsulated doxorubicin or with other antineoplastic drugs are claimed to be of therapeutic value. Also of therapeutic value in cancer eradication are claimed to be combinations of encapsulated cisplatin with a number of anticancer genes including but not limited to p53, IL-2, IL-12, angiostatin, and oncostatin encapsulated into liposomes as well as combinations of encapsulated cisplatin with HSV-tk plus encapsulated ganciclovir.